Securitized Debt Obligations, Net - Schedule of Information on Securitized Debt Obligations (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Debt Instrument [Line Items]
Interest expense on securitized debt obligations	$ 12.4	$ 10.7	$ 24.5	$ 22.7
Credit spread adjustment	0.11%		0.11%
LIBOR [Member]
Debt Instrument [Line Items]
One-month USD LIBOR	0.10%		0.10%
SOFR [Member]
Debt Instrument [Line Items]
30-day average compounded SOFR	0.03%		0.03%
Collateral Assets [Member] | Single Asset Securitization [Member]
Debt Instrument [Line Items]
Total loan amount, securitized					$ 500.0